APK patch size estimator

Estimates the size of Google Play patches and the new gzipped APK.

From two APKs it estimates the size of the new patches as well as the size of the gzipped version of the new APK, which would be used in cases where the patches are unexpectedly large, unavailable, or unsuitable. Google Play uses multiple techniques to generate patches and generally picks the best match for the device. The best match is usually, but not always, the smallest patch file produced. The numbers that this script produces are ESTIMATES that can be used to characterize the impact of arbitrary changes to APKs. There is NO GUARANTEE that this tool produces the same patches or patch sizes that Google Play generates, stores or transmits, and the actual implementation within Google Play may change at any time, without notice.

This is not an official Google product

Usage

The script uses Python 2.7.X, bsdiff and Java (you may need to install them in your system)

For the file-by-file estimation we use a jar (at /lib/file-by-file-tools.jar) generated from: https://github.com/andrewhayden/archive-patcher

To estimate the patches sizes of two APKs run:

$ python apk_patch_size_estimator.py --old-file old.apk --new-file new.apk

Output:

New APK size on disk: 18,271,850 bytes [17.4MB]  Estimated download size for new installs:
 Full new APK (gzipped) size: 16,339,603 bytes [15.6MB]  Estimated download size for updates from the old APK, using Bsdiff:
 Bsdiff patch (gzipped) size: 2,989,691 bytes [2.85MB]  Estimated download size for updates from the old APK,  using File-by-File:
 File-by-File patch (gzipped) size: 1,912,751 bytes [1.82MB]

Patches estimation process

Bsdiff estimation

File-by-file estimation

Please visit https://github.com/andrewhayden/archive-patcher for further details.

Installing external dependencies

The script uses bsdiff, gzip, head, tail, bunzip2 and java binaries, bsdiff is the only one not installed by defult in a unix based OS.

Linux debian-based

Install bsdiff:

sudo apt-get install bsdiff

OS X

Install bsdiff using Homebrew:

brew install bsdiff

Windows

The easiest way to run the script in Windows is by using Cygwin, make sure you install python and bsdiff using Cygwin's installer/setup.

Runing the unittests

Install unittest.mock

pip install mock

Run the test

python -m unittest discover tests/

Authors

Julian Toledo Andrew Hayden